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Degenerate Higher-Order Scalar-Tensor Theories
Degenerate Higher-Order Scalar-Tensor theories (or DHOST theories) are theories of modified gravity. They have a Lagrangian containing second-order derivatives of a scalar field In mathematics and physics, a scalar field is a function (mathematics), function associating a single number to every point (geometry), point in a space (mathematics), space – possibly physical space. The scalar may either be a pure Scalar ( ... but do not generate ghosts (kinetic excitations with negative kinetic energy), because they only contain one propagating scalar mode (as well as the two usual tensor modes). History DHOST theories were introduced in 2015 by David Langlois and Karim Noui. They are a generalisation of Beyond Horndeski (or GLPV) theories, which are themselves a generalisation of Horndeski theories. The equations of motion of Horndeski theories contain only two derivatives of the metric and the scalar field, and it was believed that only equations of motion of this form would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modified Gravity
{{disambiguation ...
Modified may refer to: * ''Modified'' (album), the second full-length album by Save Ferris *Modified racing, or "Modifieds", an American automobile racing genre See also * Modification (other) * Modifier (other) Modifier may refer to: * Grammatical modifier, a word that modifies the meaning of another word or limits its meaning ** Compound modifier, two or more words that modify a noun ** Dangling modifier, a word or phrase that modifies a clause in an am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lagrangian (field Theory)
Lagrangian may refer to: Mathematics * Lagrangian function, used to solve constrained minimization problems in optimization theory; see Lagrange multiplier ** Lagrangian relaxation, the method of approximating a difficult constrained problem with an easier problem having an enlarged feasible set ** Lagrangian dual problem, the problem of maximizing the value of the Lagrangian function, in terms of the Lagrange-multiplier variable; See Dual problem * Lagrangian, a functional whose extrema are to be determined in the calculus of variations * Lagrangian submanifold, a class of submanifolds in symplectic geometry * Lagrangian system, a pair consisting of a smooth fiber bundle and a Lagrangian density Physics * Lagrangian mechanics, a reformulation of classical mechanics * Lagrangian (field theory), a formalism in classical field theory * Lagrangian point, a position in an orbital configuration of two large bodies * Lagrangian coordinates, a way of describing the motions of particles o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scalar Field
In mathematics and physics, a scalar field is a function (mathematics), function associating a single number to every point (geometry), point in a space (mathematics), space – possibly physical space. The scalar may either be a pure Scalar (mathematics), mathematical number (dimensionless) or a scalar (physics), scalar physical quantity (with unit of measurement, units). In a physical context, scalar fields are required to be independent of the choice of reference frame, meaning that any two observers using the same units will agree on the value of the scalar field at the same absolute point in space (or spacetime) regardless of their respective points of origin. Examples used in physics include the temperature distribution throughout space, the pressure distribution in a fluid, and spin-zero quantum fields, such as the Higgs field. These fields are the subject of scalar field theory. Definition Mathematically, a scalar field on a Region (mathematical analysis), region ''U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Letters B
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, with its main goal being to understand how the universe behaves. "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Cosmology And Astroparticle Physics
The ''Journal of Cosmology and Astroparticle Physics'' is an online-only peer-reviewed scientific journal focusing on all aspects of cosmology and astroparticle physics. This encompasses theory, observation, experiment, computation and simulation. It has been published jointly by IOP Publishing and the International School for Advanced Studies The International School for Advanced Studies (Italian: ''Scuola Internazionale Superiore di Studi Avanzati''; SISSA) is an international, state-supported, post-graduate-education and research institute in Trieste, Italy. SISSA is active in the ... since 2003. ''Journal of Cosmology and Astroparticle Physics'' has been a part of the SCOAP3 initiative. But from 1 January 2017 it has moved out from SCOAP3 agreement. Abstracting and indexing ''Journal of Cosmology and Astroparticle Physics'' is indexed and abstracted in the following databases: References External links * Astrophysics journals IOP Publishing academic journa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horndeski's Theory
Horndeski's theory is the most general theory of gravity in four dimensions whose Lagrangian is constructed out of the metric tensor and a scalar field and leads to second order equations of motion. The theory was first proposed by Gregory Horndeski in 1974 and has found numerous applications, particularly in the construction of cosmological models of Inflation and dark energy. Horndeski's theory contains many theories of gravity, including General relativity, Brans-Dicke theory, Quintessence, Dilaton, Chameleon and covariant Galileon as special cases. Action Horndeski's theory can be written in terms of an action as S _,\phi= \int\mathrm^x\,\sqrt\left sum_^\frac\mathcal_[g_,\phi,+\mathcal_[g_,\psi_">_,\phi.html" ;"title="sum_^\frac\mathcal_[g_,\phi">sum_^\frac\mathcal_[g_,\phi,+\mathcal_[g_,\psi_right] with the Lagrangian (field theory), Lagrangian densities \mathcal_ = G_(\phi,\, X) \mathcal_ = G_(\phi,\,X)\Box\phi \mathcal_ = G_(\phi,\,X)R+G_(\phi,\,X)\left left(\Box ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ali Chamseddine
Ali H. Chamseddine ( ar, علي شمس الدين, link=no, born 20 February 1953) is a Lebanese physicist known for his contributions to particle physics, general relativity and mathematical physics. , Chamseddine is a physics Professor at the American University of Beirut and the Institut des hautes études scientifiques. Education and working positions Ali H. Chamseddine was born in 1953 in the town of Joun, Lebanon. He received his BSc in Physics from the Lebanese University in July 1973. After receiving a scholarship from the Lebanese University to continue his graduate studies in Physics at Imperial College London, Chamseddine received a Diploma in Physics in June 1974, under the supervision of Tom Kibble. After that, Chamseddine did his PhD in Theoretical Physics at Imperial College London as well, in September 1976, where he studied under supervision of Nobel Prize winner Abdus Salam. Later on, Chamseddine did his post-doctoral studies at the Abdus Salam Internationa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viatcheslav Mukhanov
Viatcheslav Fyodorovich Mukhanov (russian: Вячесла́в Фёдорович Муха́нов; born October 2, 1956) is a Soviet/ Russian born German theoretical physicist and cosmologist. He is best known for the theory of Quantum Origin of the Universe Structure. Working in 1980-1981 with Gennady Chibisov in the Lebedev Physical Institute in Moscow he predicted the spectrum of inhomogeneities in the Universe, which are originated from the initial quantum fluctuations. The numerous experiments in which there were measured the temperature fluctuations of the Cosmic Microwave Background Radiation are in excellent agreement with this theoretical prediction, thus confirming that the galaxies and their clusters originated from the initial quantum fluctuations. Later on Mukhanov proved that the results he obtained with G. Chibisov in 1981 are of the generic origin and he has developed the general consistent quantum cosmological perturbation theory. Since 2006, Mukhanov is th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Action (physics)
In physics, action is a scalar quantity describing how a physical system has dynamics (physics), changed over time. Action is significant because the equations of motion of the system can be derived through the principle of stationary action. In the simple case of a single particle moving with a constant velocity (uniform linear motion), the action is the momentum of the particle times the distance it moves, integral (mathematics), added up along its path; equivalently, action is twice the particle's kinetic energy times the duration for which it has that amount of energy. For more complicated systems, all such quantities are combined. More formally, action is a functional (mathematics), mathematical functional which takes the trajectory (also called path or history) of the system as its argument and has a real number as its result. Generally, the action takes different values for different paths. Action has dimensional analysis, dimensions of energy × time or momentu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theories Of Gravity
A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be scientific, belong to a non-scientific discipline, or no discipline at all. Depending on the context, a theory's assertions might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings. In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with the scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of it. Scientific theories are the most reliable, rigorous, and compre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
